As an exhaust gas catalyst for purifying exhaust gas discharged from an internal combustion engine, an exhaust gas catalyst configured such that a through hole is formed in a base material and a catalytic layer is provided on an inner wall surface formed by the through hole is described in the following prior art documents.
Patent Document 1 describes an exhaust gas catalyst converter configured such that catalyst carriers are placed in three stages in a casing along an exhaust gas flow direction with respective separation portions provided therebetween, and a pressure loss of each of the catalyst carriers is set to increase toward an outlet side, so that exhaust gas is stirred at the separation portions to be dispersed in a whole area, thereby improving purification efficiency.
Patent Document 2 describes an exhaust gas catalyst configured such that a catalyst portion from one side of a cell and a catalyst portion from the other side thereof are distanced from each other so as not to overlap with each other, thereby restraining an increase in a pressure loss due to the overlap between the catalyst portions.
Patent Document 3 describes an exhaust gas catalyst of which a thickness of a catalyst layer is decreased from both an upstream side and a downstream side of a through hole toward its center, so as to decrease a pressure loss of exhaust gas.